package colibri2
Weak topological orderings (WTOs) are a hierarchical decomposition of the a graph where each layer is topologically ordered and strongly connected components are aggregated and ordered recursively. This is a very convenient representation to describe an evaluation order to reach a fixpoint.
type 'n component =
| Component of 'n * 'n partition
(*A strongly connected component, described by its head node and the remaining sub-components topologically ordered
*)| Node of 'n
(*A single node without self loop
*)
Each component of the graph is either an individual node of the graph (without) self loop, or a strongly connected component where a node is designed as the head of the component and the remaining nodes are given by a list of components topologically ordered.
and 'n partition = 'n component list
A list of strongly connected components, sorted topologically
val flatten : 'n partition -> 'n list
val fold_heads : ('a -> 'n -> 'a) -> 'a -> 'n partition -> 'a